1. William S. Klug Michael R. Cummings Charlotte A
William S. Klug Michael R. Cummings Charlotte A. Spencer Concepts of Genetics Eighth Edition Chapter 13 The Genetic Code and Transcription
Copyright © 2005 Pearson Prentice Hall, Inc.

2. Figure 13-1 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-1 Flow of genetic information encoded in DNA to messenger RNA to protein.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

3. The Genetic Code Exhibits a Number of Characteristics
• linear, from mRNA
• triplet
• unambiguous
• degenerate
• start and stop signals
• commaless
• nonoverlapping
•nearly universal

4. Early Studies Established the Basic Operational Patterns of the Code
The Triplet Nature of the Code
43 = 64

5. Figure 13-2 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-2 The effect of frameshift mutations on a DNA sequence repeating the triplet sequence GAG. (a) The insertion of a single nucleotide shifts all subsequent triplet reading frames. (b) The insertion of three nucleotides changes only two codons, but the frame of reading is then reestablished to the original sequence.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

6. Figure 13-2a Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-2a The effect of frameshift mutations on a DNA sequence repeating the triplet sequence GAG. (a) The insertion of a single nucleotide shifts all subsequent triplet reading frames. (b) The insertion of three nucleotides changes only two codons, but the frame of reading is then reestablished to the original sequence.
Figure 13-2a Copyright © 2006 Pearson Prentice Hall, Inc.

7. Figure 13-2b Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-2b The effect of frameshift mutations on a DNA sequence repeating the triplet sequence GAG. (a) The insertion of a single nucleotide shifts all subsequent triplet reading frames. (b) The insertion of three nucleotides changes only two codons, but the frame of reading is then reestablished to the original sequence.
Figure 13-2b Copyright © 2006 Pearson Prentice Hall, Inc.

8. The Nonoverlapping Nature of the Code
The Commaless and Degenerate Nature of the Code

9. Studies by Nirenberg, Matthaei, and Others Led to Deciphering of the Code
Synthesizing Polypeptides in a Cell-Free System

10. Figure 13-3 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-3 The reaction catalyzed by the enzyme polynucleotide phosphorylase. Note that the equilibrium of the reaction favors the degradation of RNA, but can be “forced” in the direction favoring synthesis.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

11. Homopolymer Codes

12. Table 13-1 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Incorporation of 14C-Phenylalanine into Protein
Table Copyright © 2006 Pearson Prentice Hall, Inc.

13. Mixed Copolymers

14. Figure 13-4 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-4 Results and interpretation of a mixed copolymer experiment in which a ratio of is used
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

15. The Triplet Binding Assay

16. Figure 13-5 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-5 An example of the triplet-binding assay. The UUU triplet acts as a codon, attracting the complementary tRNAphe anticodon AAA.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

17. Table 13-2 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Amino Acid Assignments to Specific Trinucleotides Derived from the Triplet-Binding Assay
Table Copyright © 2006 Pearson Prentice Hall, Inc.

18. Repeating Copolymers

19. Figure 13-6 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-6 The conversion of di-, tri-, and tetranucleotides into repeating copolymers. The triplet codons produced in each case are shown.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

20. Table 13-3 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Amino Acids Incorporated Using Repeated Synthetic Copolymers of RNA
Table Copyright © 2006 Pearson Prentice Hall, Inc.

21. The Coding Dictionary Reveals Several Interesting Patterns among the 64 Codons

22. Figure 13-7 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-7 The coding dictionary. AUG encodes methionine, which initiates most polypeptide chains. All other amino acids except tryptophan, which is encoded only by UGG, are represented by two to six codons. The codons UAA, UAG, and UGA are termination signals and do not encode any amino acids.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

23. Degeneracy and the Wobble Hypothesis

24. Table 13-4 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Anticodon–Codon Base-Pairing Rules
Table Copyright © 2006 Pearson Prentice Hall, Inc.

25. The Ordered Nature of the Code
(similar amino acids share middle bases)
Initiation, Termination

26. The Genetic Code Is Nearly Universal

27. Table 13-5 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Exceptions to the Universal Code
Table Copyright © 2006 Pearson Prentice Hall, Inc.

28. Different Initiation Points Create Overlapping Genes

29. Figure 13-8 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-8 Illustration of the concept of overlapping genes. (a) An mRNA sequence initiated at two different AUG positions out of frame with one another will give rise to two distinct amino acid sequences. (b) The relative positions of the sequences encoding seven polypeptides of the phage
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

30. Figure 13-8a Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-8a Illustration of the concept of overlapping genes. (a) An mRNA sequence initiated at two different AUG positions out of frame with one another will give rise to two distinct amino acid sequences. (b) The relative positions of the sequences encoding seven polypeptides of the phage
Figure 13-8a Copyright © 2006 Pearson Prentice Hall, Inc.

31. Figure 13-8b Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-8b Illustration of the concept of overlapping genes. (a) An mRNA sequence initiated at two different AUG positions out of frame with one another will give rise to two distinct amino acid sequences. (b) The relative positions of the sequences encoding seven polypeptides of the phage
Figure 13-8b Copyright © 2006 Pearson Prentice Hall, Inc.

32. Transcription Synthesizes RNA on a DNA Template

33. Studies with Bacteria and Phages Provided Evidence for the Existence of mRNA

34. Table 13-6 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Base Compositions (in mole percents) of RNA Produced Immediately Following Infection of E. Coli by the Bacteriophages T2 and T7 in Contrast to the Composition of RNA of Uninfected E. Coli
Table Copyright © 2006 Pearson Prentice Hall, Inc.

35. RNA Polymerase Directs RNA Synthesis

36. Figure 13-9 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-9 The early stages of transcription in prokaryotes, showing (a) the components of the process; (b) template binding at the site involving the sigma subunit of RNA polymerase and subsequent initiation of RNA synthesis; and (c) chain elongation, after the sigma subunit has dissociated from the transcription complex and the enzyme moves along the DNA template.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

37. Figure 13-9a Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-9a The early stages of transcription in prokaryotes, showing (a) the components of the process; (b) template binding at the site involving the sigma subunit of RNA polymerase and subsequent initiation of RNA synthesis; and (c) chain elongation, after the sigma subunit has dissociated from the transcription complex and the enzyme moves along the DNA template.
Figure 13-9a Copyright © 2006 Pearson Prentice Hall, Inc.

38. Figure 13-9b Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-9b The early stages of transcription in prokaryotes, showing (a) the components of the process; (b) template binding at the site involving the sigma subunit of RNA polymerase and subsequent initiation of RNA synthesis; and (c) chain elongation, after the sigma subunit has dissociated from the transcription complex and the enzyme moves along the DNA template.
Figure 13-9b Copyright © 2006 Pearson Prentice Hall, Inc.

39. Figure 13-9c Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-9c The early stages of transcription in prokaryotes, showing (a) the components of the process; (b) template binding at the site involving the sigma subunit of RNA polymerase and subsequent initiation of RNA synthesis; and (c) chain elongation, after the sigma subunit has dissociated from the transcription complex and the enzyme moves along the DNA template.
Figure 13-9c Copyright © 2006 Pearson Prentice Hall, Inc.

40. Promoters, Template Binding, and the Sigma Subunit
Initiation, Elongation, and Termination of RNA Synthesis

41. Transcription in Eukaryotes Differs from Prokaryotic Transcription in Several Ways
Heterogeneous Nuclear RNA and Its Processing: Caps and Tails

42. Figure 13-10 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure Posttranscriptional RNA processing in eukaryotes. Heterogeneous nuclear RNA (hnRNA) is converted to messenger (mRNA), which contains a cap and a -poly-A tail, which then has introns spliced out.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

43. Table 13-7 Copyright © 2006 Pearson Prentice Hall, Inc.
Table RNA Polymerases in Eukaryotes
Table Copyright © 2006 Pearson Prentice Hall, Inc.

44. The Coding Regions of Eukaryotic Genes Are Interrupted by Intervening Sequences

45. Figure 13-11 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure An electron micrograph and an interpretive drawing of the hybrid molecule (heteroduplex) formed between the template DNA strand of the chicken ovalbumin gene and the mature ovalbumin mRNA. Seven DNA introns, A–G, produce unpaired loops.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

46. Figure 13-12 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure Intervening sequences in various eukaryotic genes. The numbers indicate the number of nucleotides present in various intron and exon regions.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

47. Table 13-8 Copyright © 2006 Pearson Prentice Hall, Inc.
Table Contrasting Human Gene Size, mRNA Size, and the Number of Introns
Table Copyright © 2006 Pearson Prentice Hall, Inc.

48. RNA Editing
Substitution editing
Insertion/deletion editing (guide RNA)

49. Transcription Has Been Visualized by Electron Microscopy

50. Figure 13-15 Copyright © 2006 Pearson Prentice Hall, Inc.
Figure Electron micrographs and interpretive drawings of simultaneous transcription of genes in E. coli (a) and Notophthalmus (Triturus) viridescens (b). (a) O.L. Miller, Jr. Barbara A. Hamkalo, C.A. Thomas, Jr. Science 169:392–395, 1970 by the American Association for the Advancement of Science. F:2.
Figure Copyright © 2006 Pearson Prentice Hall, Inc.

51. Figure 13-15a Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-15a Electron micrographs and interpretive drawings of simultaneous transcription of genes in E. coli (a) and Notophthalmus (Triturus) viridescens (b). (a) O.L. Miller, Jr. Barbara A. Hamkalo, C.A. Thomas, Jr. Science 169:392–395, 1970 by the American Association for the Advancement of Science. F:2.
Figure 13-15a Copyright © 2006 Pearson Prentice Hall, Inc.

52. Figure 13-15b Copyright © 2006 Pearson Prentice Hall, Inc.
Figure 13-15b Electron micrographs and interpretive drawings of simultaneous transcription of genes in E. coli (a) and Notophthalmus (Triturus) viridescens (b). (a) O.L. Miller, Jr. Barbara A. Hamkalo, C.A. Thomas, Jr. Science 169:392–395, 1970 by the American Association for the Advancement of Science. F:2.
Figure 13-15b Copyright © 2006 Pearson Prentice Hall, Inc.